Filoviruses include some of the most notorious human pathogens and cause significant morbidity and mortality due to severe hemorrhagic fever syndromes. Unfortunately, very few therapeutic agents are available to treat infections with these viruses. The goal of this application is to use a cell-based assay developed in Phase I to screen for compounds with antiviral activity against filoviruses such as Ebola and Marburg viruses. Significant advances have been made in identifying the cis-acting elements and tram-acting factors involved in replication of many pathogenic negative-strand RNA viruses, including filoviruses. We have developed an infectionindependent virus minigenome-expression system in which the expression of an easily measurable enzyme is dependent on the RNA replication and transcription factors that are essential for viral replication. This bioassay is amenable to high throughput screening to identify antiviral compounds. Synthetic and natural product chemical libraries have been obtained from commercial sources that use novel approaches to make diverse compounds. We will identify those compounds with the most promising chemical and biological profiles to pursue as potential anti-filovirus drugs.